Phusion Passenger Standalone is a web server that allows one to run Ruby web applications. Here are some of the highlights:
Unlike Phusion Passenger for Apache and Phusion Passenger for Nginx, Phusion Passenger Standalone does not require an external web server, it is its own and therefore extremely easy to get started.
It is powered by an Nginx core. This allows it to serve static files at blazing speeds, makes it secure enough to be directly attached to port 80, and allows it to handle slow clients. You don’t need to have Nginx already installed.
Automatically spawns and shuts down application processes. One Phusion Passenger Standalone instance can therefore handle multiple simultaneous connections and handles resource management for you. Crashing application processes are automatically restarted.
Can listen on a Unix socket, for use in reverse proxy setups.